The dispersion compensation property of octagonal photonic crystal fibers (PCFs) was simulated with multipole method in this paper.It was found that the dispersion, dispersion slope and Kappa parameter of PCFs can be designed precisely but changing the air hole size and the pitch in PCFs cladding.We compared photonic crystal fiber of hexagonal structure with that of octagonal structure, both of which have the same structure parameters. It was found that the octagonal structure easily abtains large negative dispersion and low non-linear coefficient. It was demonstrated that the octagonal structure has huge potential in designing diepersion compensation PCFs. So, we designed a novel PCF with octagonal structure.The PCF achieves a negative dispersion of -1434.9 ps·nm-1·km-1 and a negative dispersion slope of -4.6338 ps·nm-2·km-1 at λ=1.55 μm, which is far better than the conventional fibre.